Human immunodeficiency virus (HIV) infection confounds the immune response. Untreated HIV infection usually leads to a state of general immunosuppression, the acquired immune deficiency syndrome (AIDS), and susceptibility to otherwise innocuous opportunistic infections. However, to establish a successful infection and replicate, the virus has to evade immune control, a task that HIV accomplishes by using a broad array of mechanisms.
HIV, like other enveloped viruses, requires a fusion of the viral membrane with the host cellular membrane in order to enter and infect target cells. For that purpose it employs a fusion protein, the transmembrane glycoprotein gp41, which is non-covalently linked to the surface glycoprotein gp120. Together, gp120 and gp41 form the envelope glycoprotein complex which is embedded in the viral membrane as a trimer. The surface gp120 is primarily involved in recognition of cellular receptors, whereas gp41 is anchored to the viral membrane and mediates membrane fusion.
The gp41 Protein
The gp41 protein is composed of cytoplasmic, transmembrane, and extracellular domains (Chan et al., Biochim. Biophys. Acta. 1614, 36-50, 2003). The extracellular domain (ectodomain) contains four major functional regions: closest to the viral membrane is the tryptophan-rich membrane proximal ectodomain region, followed by a C-terminal heptad repeat, an N-terminal heptad repeat, and a stretch of 16 hydrophobic residues, located in the N terminus, termed fusion peptide (FP) (FIG. 1). During the initial step of the membrane fusion process, FP anchors gp41 to the target membrane. In the next step, the gp41 heptad repeat domains interact with each other to form a six-helix bundle conformation and bridge the gap between the opposing membranes and eventually complete the fusion process.
International Patent Application No. WO 2005/060350 of one of the inventors of the present invention, discloses membrane binding diastereomeric peptides comprising amino acid sequences corresponding to a fragment of a transmembrane protein, having at least two amino acid residues of the diastereomeric peptides in a D-isomer configuration, useful in inhibiting fusion membrane protein events, including specifically viral replication and transmission. WO 2005/060350 discloses, inter alia, the use of diastereomeric peptides corresponding to amino acids 512 to 544 of HIV-1 gp41 and to amino acids 638 to 673 of HIV-1LAV gp41 for inhibiting membrane fusion processes.
In addition to its role in mediating the actual fusion event, gp41 has been shown to contain two immunosuppressive regions that are believed to suppress the HIV-specific immunity. The first is the above mentioned N terminus hydrophobic region known as the fusion peptide (FP) (Quintana et al., 2005, J. Clin. Invest. 115, 2149-2158; Cohen, 2008, Biochemistry 47, 4826-4833) and the second is the 583-599 region known as immunosuppressive peptide (ISU) (Ruegg et al., 1989, J. Virol. 63, 3257-3260). Interestingly, the mechanisms by which these two immunosuppressive peptides exert their activity are different. The FP inhibits antigen-specific T-cell proliferation by specifically interacting with the T-cell receptor α subunit (TCRα), whereas the ISU inhibits T-cell proliferation induced by anti-CD3 antibodies or by Phorbol Myristate Acetate (PMA)/ionomycin (Ruegg et al., 1989, J. Virol. 63, 3250-3256).
International Patent Application No. WO 2006/077601, to some of the inventors of the present application, provides peptides derived from the HIV gp41 FP domain useful for prevention or treatment of autoimmune and other T cell-mediated pathologies. WO 2006/077601 further provides novel peptides derived from the HIV gp41 FP domain.
International Patent Application No. WO 2010/017209, published after the priority date of the present application, discloses isolated immunogens including variant hepatitis B surface antigens (HBsAgs) wherein the transmembrane domain of the HBsAg is replaced with a gp41 antigenic insert. Particularly, the antigenic insert includes an antigenic polypeptide fragment of gp41 including the membrane proximal region of gp41 and a transmembrane region of gp41. According to the '209 application, the variant HBsAgs may be used for inducing an immune response to HIV-1.
Mutations in the membrane spanning domain of the HIV envelope glycoprotein were shown to affect fusion activity (Owens et al., J. Virol. 68 (1): 570-574, 1994; Helseth et al., J. Virol. 64 (12): 6314-6318, 1990). Recently, Kim et al. studied gp41 transmembrane domain stability in different environments (lipid or water) via mutating glycine 691, 695 and arginine 697 (Kim et al., Biochimica et Biophysica Acta 1788, 2009, 1804-12).
U.S. Pat. No. 5,756,666 provides peptides capable of inducing immune response to HIV, the peptides being fragments of HIV having a sequence of 8 to 11 amino acid residues corresponding to an HLA-binding motif, wherein said peptides bind to HLA and induce killer cells capable of attacking HIV-infected cells as target cells.
U.S. Pat. No. 5,556,744 provides a panel of HIV peptides derived from gp120 and gp41, pharmaceutical and vaccine compositions containing same useful in diagnosing whether or not a patient is of vertical HIV transmission status, methods for diagnosing same and methods for identifying epitopes and peptides associated with non-transmission status. U.S. Pat. No. 5,981,706 is directed to methods for synthesizing heat shock protein (HSP)-peptide complexes comprising the steps of adding a shock protein to a denatured protein matrix to bind the HSP to the denatured protein matrix; and adding a complexing solution comprising a peptide to elute a HSP-peptide complex. The '706 publication further provides the HSP-peptide complexes and an apparatus for synthesizing said complexes. Among the peptides suitable for use as complexing agents, according to the '706 publication, are gp41 derived peptides.
T Cells
The activity of T cells is regulated by antigen, presented to a T cell in the context of a major histocompatibility complex (MHC) molecule. The T cell receptor (TCR) then binds to the MHC-peptide complex. Once antigen is complexed to MHC, the MHC-antigen complex is bound by a specific TCR on a T cell, thereby altering the activity of that T cell. The TCR complex is thus an attractive target for immunomodulation.
The TCR complex of the majority of the mature T cells is a TCRαβ heterodimer associated to the γ, β, ε and ζ chains of CD3. This complex is stabilized by interactions between the transmembrane domain of the TCR chains and CD3 subunits. The interaction of the TCR with a peptide presented by MHC induces a conformational change in the TCR that triggers CD3 phosphorylation.
While the normal immune system is closely regulated, aberrations in immune responses are not uncommon. In some instances, the immune system functions inappropriately and reacts to a component of the host as if it were, in fact, foreign. Such a response results in an autoimmune disease, in which the host's immune system attacks the host's own tissue. T cells, directly or indirectly affect such autoimmune pathologies.
Numerous diseases are believed to result from autoimmune mechanisms. Prominent among these are rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis, Type I diabetes, myasthenia gravis, pemphigus vulgaris. Autoimmune diseases affect millions of individuals worldwide and the cost of these diseases, in terms of actual treatment expenditures and lost productivity, is measured in billions of dollars annually.
T cells also play a major role in the rejection for organ transplantation or graft versus host disease by bone marrow (hematopoietic stem cell) transplantation. Regulation of such immune responses is therefore therapeutically desired.
Traditional reagents and methods used to attempt to regulate an immune response in a patient result in unwanted side effects and limited effectiveness. For example, immunosuppressive reagents (e.g., cyclosporin A, azathioprine, and prednisone) used to treat patients with autoimmune diseases also suppress the patient's entire immune response, thereby increasing the risk of infection, and can cause toxic side effects to non-lymphoid tissues. Due to the medical importance of immune regulation and the inadequacies of existing immunopharmacological reagents, reagents and methods to regulate specific parts of the immune system have been the subject of study for many years.
A method of treating or inhibiting symptoms of an autoimmune disease by administering a sub-immunogenic amount of an antigen more immunoreactive with alloimmune-immunogen-absorbed (AIA) serum as compared to nonimmune serum of the same species was disclosed in U.S. Pat. No. 5,230,887. One putative antigen, based on its purported serological cross reactivity with MHC Class II antigens, was suggested to be intact gp41 of HIV. The alleged cross reactivity resides in a C-terminal peptide.
International Patent Application No. WO 2007/034489, to one of the inventors of the present application, provides immunogenic compositions comprising the T-Cell Receptor constant domain and peptides derived therefrom, effective in preventing or treating T cell mediated inflammatory disease. The immunogenic compositions of WO 2007/034489 comprise at least one immunogen selected from the group consisting of: (i) an isolated constant domain of a chain of a human TCR; and (ii) a peptide comprising an immunogenic fragment of the constant domain of a chain of a TCR.
International Patent Application No. WO 2007/034490 provides diastereomeric peptides and lipopeptides derived from the T cell receptor alpha (TCRα) transmembrane domain (TMD), pharmaceutical compositions comprising same, and uses thereof for therapy of T cell mediated inflammatory diseases.
Monocytes and Macrophages
Monocytes are critical effectors and regulators of the innate immune response, as well as in the adaptive immune response of vertebrate animals. Monocytes, and their differentiated cells, macrophages, are phagocyte cells which reside in various tissues and are among the first cells of any organ to be exposed to infectious agents and to become activated in response to an insult. Upon activation macrophages participate actively in the onset of inflammation by releasing cytokines that amplify the initial inflammatory response. Monocytes and macrophages are the prime immune cells managing inflammatory responses, which contribute to development of number of diseases and disorders such as cancer, sepsis, asthma and diabetes.
The Tumor Necrosis Factor (TNF) family of cytokines plays an essential role in multiple biological functions including inflammation, organogenesis, host defense, autoimmunity, and apoptosis. TNF-α is a central proinflammatory cytokine and plays an important role in various pathophysiological functions, being such as cell growth, differentiation and death. TNF appears not only to orchestrate acute responses to infection and immunological injury but also to act as a balancing factor required for the re-establishment of physiological homeostasis and regulation.
Despite the approval of TNF as an anticancer agent, it has been implicated in both cancer development and progression in some preclinical models. In particular, as a central mediator of inflammation, TNF might represent one of the molecular links between chronic inflammation and the subsequent development of malignant disease. Furthermore, deregulated TNF expression within the tumor microenvironment appears to favor malignant cell tissue invasion, migration and ultimately metastasis formation (Mocellin and Nitti, Front. Biosci. 2008 Jan. 1; 13:2774-83). Inhibition of TNF-α mediated signaling as means for treatment cancer has been recently disclosed. For instance, inhibition of TNF-mediated signaling was demonstrated as a potent therapeutic agent for prostate cancer (Srinivasan et al. Apoptosis. 2010 February; 15(2):153-61).
None of the background art, however, discloses or suggests that peptides derived from the transmembrane domain of HIV-1 gp41 regulate T cell and/or monocyte activation, and are particularly useful in treating or preventing diseases and disorders such as autoimmune diseases and inflammatory diseases.
There exists a long-felt need for more effective means of curing or ameliorating inflammatory or autoimmune diseases, such as pathologies associated with T cell activation and/or TNF-α secretion. In addition, there exists a long-felt need for curing or ameliorating TNF-α mediated pathology.